EXECUTIVE SUMMARY ON CPU USAGE:

By default, BFGMiner will NOT mine on CPUs unless it is explicitly compiled with

support and told to do so. CPU mining for bitcoin is generally considered to be

obsolete as it requires considerably more power per hash computed than either

GPU, FPGA or ASIC based mining. If you still wish to mine using CPUs you will

need to build a custom binary with support enabled (refer to the build notes in

README for further information).

The following CPU mining options are available:

--algo <arg> Specify sha256 implementation for CPU mining:

fastauto* Quick benchmark at startup to pick a working algorithm

auto Benchmark at startup and pick fastest algorithm

c Linux kernel sha256, implemented in C

4way tcatm's 4-way SSE2 implementation

via VIA padlock implementation

cryptopp Crypto++ C/C++ implementation

cryptopp_asm32 Crypto++ 32-bit assembler implementation

sse2_32 SSE2 32 bit implementation for i386 machines

sse2_64 SSE2 64 bit implementation for x86_64 machines

sse4_64 SSE4.1 64 bit implementation for x86_64 machines

altivec_4way Altivec implementation for PowerPC G4 and G5 machines

--cpu-threads <arg> Number of miner CPU threads (default: -1)

CPU FAQ:

Q: What happened to CPU mining?

A: Being increasingly irrelevant for most users, and a maintenance issue, it is

no longer under active development and will not be supported unless someone

steps up to help maintain it. No binary builds supporting CPU mining will be

released for Windows but CPU mining can be built into BFGMiner when it is

compiled. For builds which do support CPU mining, it is still disabled by

default, and must be enabled using the -S cpu:auto option.

Q: So, should I even try CPU mining?

A: No, it honestly will waste more power and time than it is worth at this stage.

If you really wish to mine, you are better off getting a suitable ASIC instead.

Q: But, if the computers aren't mine and I'm not paying for the power?

A: If you are trying to use computers that aren't yours, you really should

reconsider. Attempting to mine with a large number of devices will often impact

negatively on many pools and will likely pay almost nothing due to the small

number of successful shares submitted. Apart from that, you will probably get

into trouble with someone down the track for misusing the computers.